Catalyst system and method for carbonylation reaction

A catalyst system for a carbonylation reaction, comprising the following components:

• (a) a Group VIII metal or a compound of a Group VIII metal;
• (b) a bidentate phosphine ligand;
• and
• (c) an acidic additive;
• wherein the bidentate phosphine ligand as component (b) is represented by the following formula (I):
• wherein P represents a trivalent phosphorus atom;
• Ar represents an aromatic group, A and B each represent a single bond or alkylene, and A and B are located at ortho positions on the Ar group;
• each of R1 and R2, together with the P atom attached thereto, form a monocyclic group that is a phospha monocyclic group having at least 3 carbon atoms on the ring;
• the monocyclic group is selected from following groups with or without a substituent:
• an alicyclic group, a lactone group, a lactam group, a cyclic ketone group, a heterocyclic group containing at least one N atom, or a heterocyclic group containing at least one O atom;
• the substituent is alkyl, cycloalkyl, substituted or unsubstituted aryl, a halogen atom, a nitrogen-containing group or an oxygen-containing group;
• and the substituent is attached to the monocyclic group via a single bond or by sharing a plurality of carbon atoms.